The semiconductor industry uses several different coordinate systems for wafer related data interpretation. Many different coordinate systems are used because common coordinate systems (e.g., Cartesian or polar) alone cannot fulfill the requirements of all semiconductor manufacturing processes. Each system reflects the specific technical requirements of the particular process or design stage of the semiconductor fabrication process and is used to describe wafer related process measurements and controls. Thus, the different coordinate systems must be supported throughout the fabrication process from the design phase to the final test sequences.
Example processes used in the fabrication of integrated circuits include lithography, metrology, chemical mechanical polishing (CMP), design center, and mask house. Lithography uses a field-based coordinate system defined by the exposed field, which has the same orientation as the wafer. Lithography utilizes a center field vector and an intra field vector to identify positions on a wafer. Metrology operates at the chip level using a die map based coordinate system with a die index (row, column) and an intra die coordinate in the wafer orientation.
In general, process tools define coordinate systems based on the semiconductor device designs, desired data output and location specificity desired for process refinements and controls. Metrology, for example, utilizes orthogonal coordinates based on x-y translation of the wafer stages. CMP is based on tool mechanics and uses radial coordinates for defining target positions due to the rotational movement of the CMP tools. The data from CMP tools are wafer related coordinates in a polar coordinate system separated into regions with several radius ranges. Design center process tools operate at the chip and field level with a base orientation, which is defined by the design. Since the chip may be rotated on a mask, a combination of different coordinate systems may be used. Mask house process tools utilize a field based coordinate system having a predefined orientation (e.g., intra field and intra die). Other coordinate system may be used for other fabrication processes.
Since different coordinate systems are used for identifying different locations on a wafer, in each process step, external software is needed to interconvert the coordinate systems to define a position on the wafer accurately. Conventional manual conversion processes are time consuming and generally several repeated conversions are required, adversely affecting conversion accuracy. Tools used in the semiconductor manufacturing process need to recognize displacement precisely (e.g., on the order of nanometers). However, each tool may be based on a particular type of movement when processing the wafer in accordance with a specific coordinate system.
Due to the presence of many different kinds of software tools, a coordinate conversion system is required for a tool to be accurately displaced. Tool companies may provide conversion software as add-ons. However, these add-ons do not extend beyond one or two possible conversions and do not cover all of the conversions needed. Furthermore, multiple conversions require high effort for all software tools to be developed and maintained. As device geometries shrink and wafer sizes increase, the system may become overloaded with context-based information for each tool/process step in the fabrication.
What is needed is a method and apparatus for performing coordinate system conversions for semiconductor processing that can efficiently convert one coordinate system to another coordinate system using limited computational resources.